Hello. This situation came up during my game last evening: I declear a Fireteam Order, with the leader being the teams Killer Hacker. The Fireteam includes a repeater, which during the end of the first short skill ends in range of an enemy Killer Hacker, but none of the other models. The enemy Killer Hacker now has an ARO; can he hack the Fireteam Killer Hacker through her repeater? What reactions are possible for the enemy Killer Hacker? I believe I read somewhere that you cannot use opposing team's repeaters in the reactive turn, but I can't seem to find it any longer.
You can definitely hack through enemy repeaters on either active or reactive turn. However, doing so imparts a -3 penalty to the hacker trying to hack through said enemy repeater. However, however, Killer Hackers ignore this malus.
You can, no problem with that. That's why, when you have a good repeater network (let's say : nomads), you have to be extra careful before using entire order program (or a KHD will fry your head)